The urographic findings in acute pyelonephritis: non-obstructive hydronephrosis.

Excretory urography was performed on 4 patients early in the course of acute pyelonephritis. These studies showed dilatation of the involved collecting system without obstruction. The dilatation resolved after therapy in 3 patients and was not present on a previous excretory urogram in the fourth. Although previous studies have shown that the excretory urogram is usually normal in cases of acute pyleonephritis these cases demonstrate that this disease can produce dilatation of the collecting system and mimic obstruction.